Automatic switched optical network (ASON) is a new generation optical network which realizes an automatic switching function under the control of routing and signaling, and is a standardized intelligent optical transport network. The ASON introduces an independent control plane on the basis of the original management plane and transport plane of the conventional synchronous digital hierarchy (SDH) network, and introduces the signaling and routing into a transport network for the first time, so as to converge three fields of switching, transporting and data by establishing a call and a connection via the intelligent control plane, and therefore achieve a routing setting, an end-to-end service dispatching and an automatic network recovery.
The Constrained Shortest Path First (CSPF) algorithm is one of path algorithms that are frequently used in the field of ASON. Typically, when the CSPF algorithm is used to calculate a path, the minimum weight path is obtained by accumulating link weights configured by a network manager based on the Dijkstra algorithm, or the only factor taken into consideration is to reduce the hops to the least, which generally leads to an over-centralization on some links and a consequent unbalanced distribution of network traffic in the whole network. Therefore, it is a possible consequence that, on the one hand, some certain links bear excessive services; on the other hand, the majority of the other links are in idle state.
In order to achieve a balanced load, a great many of theoretical algorithms can be employed to select a network path, such as the round-robin algorithm, the least-connection algorithm, the response time algorithm, the hash algorithm, the least connection error algorithm, the link bandwidth algorithm and so on. At present, the simplest method for realizing the balanced load based on the link bandwidth algorithm is to perform a simple weighting processing on a link, that is, increase the weight of each link on the path through which an established service passes by 50 or 100, and select the minimum weight link in the next path calculation, so as to avoid multiple services passing through the same path effectively.
In related art, the Chinese patent application No. CN200810116520.3 has proposed a method for realizing the balanced load. In the method, a load index is introduced to select an optimal path from multiple non-intersected paths. The method has taken into consideration the bandwidth of the whole path rather than the bandwidth of a single link. Although the method possesses the characteristic of macroscopically and comprehensively planned, its realization is complicated. The method requires executing the Dijkstra algorithm for many times to calculate the non-intersected paths based on a new network topology structure, therefore, the realization of the algorithm is of high complexity and the efficiency is low. Furthermore, the method takes the selectable bandwidth of the link in a path with the minimum selectable bandwidth as the maximum bearable load of the path, whereas the influence of the selectable bandwidths of the other links in the path on the load of the whole network is not taken into full consideration. Therefore, the method sonly realizes the balanced load among paths rather than among the links of the whole network.